Effects of Zr Doping on Anti-Ca Poisoning of the Ce–Mn/3DOM-m Ti–Zr Catalyst for Low-Medium-Temperature NH₃-SCR of NO_<i>x</i>

The development of catalysts with high NH3-selective catalytic reduction (SCR) activity in the presence of calcium (Ca) is urgently required for cement kiln flue gases at low-medium temperatures. Herein, a novel Ce–Mn/3DOM-m Ti–Zr (CMZT-3DOM-m) catalyst was synthesized for low-medium-temperature NH3-SCR. Over 90% NOx conversion can be obtained at 125–275 °C with over 95% N2 selectivity, accompanied by the excellent wide-temperature NH3-SCR performance and superior resistance to Ca. Through scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), temperature-programmed reduction with H2 (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterizations, the results demonstrated that Zr doping could effectively mitigate grain growth and enlarge the surface area of the CMZT-3DOM-m catalyst. Furthermore, the surface acidity, redox properties, concentration of surface Ce3+, Mn4+ and chemisorbed oxygen were significantly improved. In situ DRIFTS experiments demonstrated that the adsorption and activation of NH3 and NO are conducive to the excellent resistance to Ca poisoning. As a sacrificial site for Ca binding, Zr protected the active species, thereby enhancing the catalyst’s resistance to Ca poisoning and demonstrating excellent anti-Ca properties, which offered a novel approach to the design of catalysts for the prevention of Ca poisoning at low-medium temperatures.